personally, here's something I see as both a fun game, and perhaps a help with this sort of mod.
1)Identify a random event in history, of at least mild to significant importance. The longer the event occured before the mod's time period, the more difficult
2)Change the outcome. This can either be a simple "yes/no" or "win/lose" change, or more complex.
3)Get with some friends, or do this by yourself: Try and muse out the ripple effects on history, including both empires and technology. Try and get to the date at which your mod takes place.
4)Set up the mod conflict with what you have....and then reflect on how wildly powerful even a small change is!
I once tried this with the Ottoman Invasions, Prussian Wars, and Genghis Khan with some pals....and things turned out weird O.O